Will Low-Carb Diets Ultimately Make Us Fat?

Many low-carb diets emphasize eating only "good" carbs from fruits, vegetables, and whole grains, but supermarkets are being flooded with low-carb junk food.

By Dulce ZamoraWebMD Feature

Reviewed By Brunilda Nazario

At 36 years old, Nicola Myrie received a stern warning from her doctor. Lose weight or risk a cardiac event in six or seven years. The New York City accountant immediately went on her own diet of watchful eating. After four months, she despaired at shedding only 6 of her weight loss target of at least 40 pounds.

Then her cardiologist suggested The South Beach Diet, a multistage approach to weight loss starting with a low-carb plan and later allowing the addition of "good carbs." In three months, Nicola dropped 22 pounds and found significant improvements in her blood pressure, cholesterol, and homocysteine levels - a blood chemical linked to inflammation and heart disease.

"I feel fantastic, like I'm in my 20s again," says Nicola, remarking on her renewed confidence and energy. Once she loses 20 more pounds, she vows to maintain some of the South Beach Diet's principles of eating throughout her life.

Friend or Fad?

If health and food experts are right, Nicola's lifelong plan may not materialize.

Hundreds of studies have shown that restrictive diets like the low-carb plan don't keep the weight off in the long run, says Mark Kantor, PhD, associate professor of nutrition and food science at the University of Maryland. He predicts that the popularity of low-carb diets will last no more than five years.

A spokeswoman for the American Dietetic Association agrees. "Anything that you have to adhere to has to be un-adhered to at some point," says Lisa Dorfman, MSRD. "People live normal lives. They go to vacation; they go to parties; they have social lives. The problem is that many of those [low-carb] programs don't accommodate those natural and normal life needs."

Dorfman sees the low-carb craze waning and likens it to the low-fat fad of the '90s. A decade ago, the low-fat trend created a stir that not only demonized fat, but also produced hundreds of products that reduced or eliminated it.

Low-carb advocates beg to differ. "To call it a fad is to ignore history," says Matthew Wiant, senior vice president and chief marketing officer for Atkins Nutritionals Inc. "Low-carb diets were popular for the first couple of million years people were on the planet. It's only been since the advent of agriculture and refined food products that higher-carb diets have become the norm."

Wiant points to several short-term studies that show the benefits of low-carb diets: quick weight loss and improved cholesterol levels. To counter the naysayers, he says there have been long-term studies (12 months long) of the diet that demonstrate sustained weight loss without increasing their risk of heart disease.

Yet Kantor expects research to someday catch up with the ills of low-carb diets. "In the long term, there is no question that low-carb diets will be shown to be dangerous," he says, noting that hundreds of epidemiological studies around the world have demonstrated that high-carbohydrate foods such as fruits, vegetables, and whole grains reduce risk of heart disease and prevent cancer.

Wiant responds in defense of low-carb diets. "It's irresponsible to conclude, based on the data out there, that the long-term studies will show some kind of huge reversal of [improved cholesterol] numbers," he says.

Food Fight

At the heart of the food fights on what will sustain weight loss and lower heart disease risk is the indisputable fact that American waist sizes are expanding.

According to the National Center for Health Statistics, 64% of adults aged 20 years and older are overweight or obese, a 20% jump from the early 1960s. In preteens and teenagers, the numbers of overweight are both at 15%, compared with about 4% each 40 years ago.

The figures are especially alarming given that risks of developing diabetes and heart disease increase with weight.

Experts blame a sedentary lifestyle and bigger food portion sizes for the bulge. But there is also some finger pointing at the role of processed foods and junk food such as white breads, white rice, pasta, soda, chips, and cookies.

Wiant says many of the low-fat products caused weight gain because manufacturers added carbohydrates to the food to make up for the lack of fat.

Low-carb critics could apparently make the same argument. In order to replace carbohydrates, food makers have had to add fat, protein, fiber, water, or sugar-free sweeteners.

"You can't have a low-fat, low-carbohydrate, low-protein food, because then, what have you got?" says George Bray, MD, Boyd Professor in the division of nutrition and chronic diseases at the Pennington Biomedical Research Center in the Louisiana State University system. "Whenever someone lowers something, there's been a relative replacement by something else."

The sugar alcohols in many low-carb products -- namely sorbitol, mannitol, and maltitol -- particularly concern Roger Clemens, PhD, a food science communicator for the Institute of Food Technologists. Although the sweeteners have been shown to be generally safe, Clemens worries about the presence of the sugar alcohols in so many foods.

"The sweeteners were never intended for larger quantities," he says, noting that some people may experience stomachaches, gas, and diarrhea with greater consumption of such products.

Other low-carb ingredients such as fiber and soy can also cause gastrointestinal distress, warns Dorfman.

License to Eat

There are those who believe that the low-fat movement of the 1990s actually encouraged weight gain. Because people thought they were eating low-fat products, they reportedly ate more. Some food experts fear the same trend could happen with low-carb goods.

Katherine Tallmadge, also a spokesperson for the American Dietetic Association, is no fan of low-carb diets. Yet she does say the one good thing about them is that they initially kept people away from processed foods.

"Unfortunately, the trend is starting to undo itself," she says, pointing to the wave of low-carb junk food. "The one benefit of that diet is being undone with all of these low-carb products."

The folks at Atkins say they cannot account for other low-carb products, but foods with their company name are scientifically tested to meet the diet's requirements.

Plus, Atkins products are not meant to replace whole foods, says Matt Spolar, vice president of product technology. "Idealistically, yes, people should only focus on healthy fruits and vegetables, whole foods, and healthy meats," he says. "But the American consumers go up and down the aisles of the supermarket and buy other products. We want to provide them with an alternative."

When buying low-carb goods, Dorfman suggests looking at the food's total calorie content, total fat, fiber content (to avoid frequent bathroom visits), and any substitutes such as soy and sweeteners.

It's also important to keep in mind that there is no marketplace standard for low-carb products. The FDA is working on definitions for the terms "low carb," "reduced carb," and "carb-free." Until the agency comes up with a ruling, it's up to the consumer to decipher the meaning of carb-conscious edibles.